Closure assembly for a wide mouth vessel

ABSTRACT

A closure assembly includes: a vessel opening; a closure for said opening, the closure having a base portion and a skirt portion; a first screw thread on the opening, said first screw thread having one or more first thread segments; a second screw thread on an inner surface of the skirt of the closure, said second screw thread having one or more second thread segments; said first and second screw threads being configured to enable a user to secure, remove and resecure the closure into a sealing position on the opening by rotation of the closure on the opening; wherein the first thread segments are shorter than said second thread segments; and wherein the second thread segments are each made up of one or more radially spaced projecting portions, each said portion extending radially no more than about 60° around the closure skirt.

TITLE OF THE INVENTION BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improved threaded closure assembliesfor wide mouth vessels, in particular for drinking vessels. Theinvention also provides improved threaded closure caps for use in suchassemblies.

2. Description of Related Art

The term “drinking vessel” refers to a container having an opening atthe top sufficiently large to allow a liquid to be sipped from theopening. For example it may be a drinking glass or cup. The presentinvention allows a range of everyday drinking glass and cupconfigurations to be fitted with secure, leak-tight and optionally alsopressure tight closures. It will be appreciated that the closureassemblies of the present invention are also suitable for a range ofother wide-mouth containers, especially those for the storage ofmaterials under pressure.

Current commercially mass-produced beverage containers use threads onthe container neck and closure of the continuous, helical type. Thethreads comprise a single, substantially continuous thread portion onthe container neck with a low thread pitch angle, typically less than5°. The low pitch angle is needed in order to ensure that the closuredoes not unscrew spontaneously. The low pitch angle also provides thenecessary leverage to achieve an air tight compressive seal between theclosure and the container neck when the closure is tightened onto thecontainer neck. The low pitch of the helical threads also means that theclosure typically needs to be rotated through more than 360° todisengage it completely from the container neck.

Drawbacks of these low pitch helical threads include the laboriousrotation required to remove and resecure the closure on the neck,excessive use of molding material to form the long helical threads, andunreliable separation of tamper-evident rings from the closure skirt dueto the low pitch angle of the threads. The difficulty of securing theclosure on the neck is especially severe for drinking vessels, since thevery low-angle threads needed for large openings are easily crossed.Furthermore, the problem of excessive use of molding material isespecially severe for the larger opening of a drinking vessel.

The present applicant has described an improved pressure safety closurefor carbonated beverage containers in International Patent applicationWO95/05322. This application describes container closure assemblieshaving substantially continuous threads defining a substantiallycontinuous helical thread path, although the pitch of the helix canvary. The closure can be moved from a fully disengaged to a fullysecured position on the container neck by rotation through 360° or less.The threads on the neck or the closure are provided with mutuallyengageable elements to block or restrict rotation of the closure in anunscrewing direction beyond an intermediate position when the closure isunder an axial pressure in a direction emerging from the container neck,the neck and closure being constructed and arranged to provide a ventfor venting gas from the container neck at least when the closure is inthe intermediate position. This pressure safety feature prevents theclosure from blowing off uncontrollably once unscrewing of the closurefrom the container neck has started. It thus allows the use of shorter,more steeply pitched or multiple-start threads in the container andclosure assembly, thereby rendering the assembly much more elderly- andchild-friendly without sacrificing pressure safety. WO97/21602 andWO99/19228 describe improved versions of the assemblies of WO95/05322.

The beverage container closure assemblies exemplified in WO95/05322 haveshort projecting thread segments on the cap and longer (but still shortrelative to conventional low-pitch closure assemblies) projecting threadsegments on the container neck. This arrangement is conventional, inpart because of the requirements of high-speed injection molding of thecaps, according to which the caps must be “bumped” off a (preferably)one-piece mold mandrel with minimum distortion.

Interestingly, the various screw-top formats for beverage containershave not yet completely replaced glass bottles with crown closures. Thisis despite the fact that crown closures require a bottle opener to open,and cannot be resecured on the bottle neck in airtight fashion, therebymaking it necessary to consume the whole contents of such a bottleimmediately after opening.

The present applicant considers that one of the reasons for thecontinued use of crown closures is that they are better suited forconsumption directly from the bottle because the relatively smoothsurfaces of the bottle neck are more comfortable between the consumer'slips. This characteristic will be referred to as the “user-friendliness”of the bottle neck. In contrast, screw top container necks have neckthreads that present a relatively rough or abrasive surface to the lips.

It is an object of the present invention to provide improved screw topclosure assemblies for drinking vessels. The present invention isespecially applicable to drinking vessels containing beverages,including carbonated beverages.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a threaded closure assembly for adrinking vessel comprising: a threaded opening (neck) at the top of thedrinking vessel; a closure for said opening, the closure having a baseportion and a skirt portion; a first screw thread on the opening, saidfirst screw thread comprising one or more first thread segments; asecond screw thread on an inner surface of the skirt of the closure,said second screw thread comprising one or more second screw threadsegments; said first and second screw threads being configured to enablea user to secure, remove and resecure the closure onto a sealingposition on the opening by simple rotation of the closure on theopening; wherein said first thread segments are shorter than the secondthread segments, and wherein the second thread segments are each made upof a plurality of radially spaced projecting portions, each said portionextending radially no more than about 60° around the closure skirt.

The term “drinking vessel” refers to a container having an opening(neck) at the top sufficiently large to allow a liquid to be sipped fromthe opening. Normally the opening of a drinking vessel has an insidediameter of at least about 3 cm, preferably from about 4 cm to about 10cm, and more preferably from about 5 cm to about 8 cm. The opening isnormally substantially cylindrical. The present invention is alsoapplicable to other wide-mouth containers having openings with thesepreferred diameters.

In certain embodiments the drinking vessel has a substantially tubularshape, for example it may in the shape of a drinking glass. In certainembodiments, the opening at the top has an area of at least about 50% ofthe area of the base of the vessel, preferably at least about 80% of thearea of the base of the vessel, and in certain embodiments the area ofthe opening at the top of the vessel is greater than the area of thebase of the vessel.

The drinking vessel, is preferably formed from thermoplastic material,that is to say from a molded polymer, but it may be formed from glass.The threaded opening is preferably formed in one piece with the drinkingvessel.

The closure is preferably made from injection-molded thermoplastic, andit is a particular advantage of the present invention that the closurescan easily be manufactured by high-speed injection molding, as will bedescribed further below.

Preferably, there are at least four of said first thread segments. Inthe larger opening formats especially there may be eight, twelve,sixteen or more of the first thread segments. The number of secondthread segments is typically the same as the number of first threadsegments. Preferably, this results in a number of thread starts equal tothe number of first thread segments, or preferably at least two threadstarts, more preferably at least four, most preferably eight, twelve,sixteen or more thread starts.

The first thread segments on the opening are shorter than the secondthread segments. That is to say, they extend radially around the openingby a lesser angle than the angle through which the second threadsegments extend around the closure skirt. The first thread segments donot extend all the way around the opening, and normally they do notoverlap around the opening. Preferably, at least one of the first threadsegments extends circumferentially from about 1 to about 30 degreesaround the opening, more preferably from about 2 to about 15 degrees,more preferably from about 3 to about 10 degrees, and more preferablyall of the first thread segments so extend. Preferably, the maximumlength of each first thread segment is from about 2 to about 20 mm, morepreferably from about 4 to about 15 mm, more preferably from about 6 toabout 12 mm. Preferably, at least about 40% of the circumference of theopening is free of the first thread segments, more preferably from about50% to about 95% of the circumference of the opening is free of thethread segments. The absence of the thread segments from the major partof the circumference of the opening increases the user-friendliness ofthe opening.

Preferably, all of the first thread segments have substantially the sameshape and configuration, whereby the number of thread starts may beequal to the number of first thread segments.

The term “first thread segment” typically refers to an elongate, pitchedprojection on the outside of the opening. It preferably does not referto a simple projecting boss or peg. The mean pitch of the first threadsegment surfaces is preferably from about 5° to about 25°, morepreferably from about 10° to about 20°. The upper and lower surfaces ofthe first thread segments may have different pitches, and the pitchalong one or other of said surfaces may also vary. Preferably, at leastone of said surfaces has at least one constant pitch region extendingfor at least about 2 mm, preferably about 5 mm to about 20 mm around theopening. For example, the first thread segment may be a short helicalthread segment having rounded ends, similar to the thread segments onthe closure caps described in detail in WO95/05322 or WO97/21602.

The first thread segments may be substantially triangular, rectangular,rounded or chamfered rectangular, or trapezoidal in cross-section alongthe longitudinal axis of the vessel. Preferably, the first threadsegments are smoothed. That is to say, at least one edge of the segmentsis shaped to present a rounded or chamfered cross-section along thelongitudinal axis of the vessel instead of a triangular, rectangular ortrapezoidal cross-section between the side of the segment and the top ofthe segment. Preferably, substantially all of the edges of the segmentare smoothed in this way. Preferably, this results in an increasedradius of curvature between the top of the segment and the side of thesegment relative to the prior art. For example the radius of curvaturemay be at least 0.5 mm, more preferably at least 1 mm or 2 mm.Preferably, the cross-section of the segments taken along thelongitudinal axis of the vessel is a substantially continuous curve suchas a semicircle or sinusoidal curve. This smoothed profile improves theuser-friendliness of the opening thread finish.

Preferably, the maximum radial height of the first thread segments abovethe cylindrical base of the thread finish on the opening is greater than0.1 mm, more preferably greater than 0.2 mm and still more preferablyfrom 0.5 to 3 mm, most preferably from 1 to 2 mm. Preferably, the widthof the first thread segments (measured along the longitudinal axis ofthe vessel) is from 1 mm to 6 mm, more preferably from 2 mm to 4 mm. Theuse of such relatively large and high thread segments helps make itpossible to produce a user-friendly neck finish onto which a suitablescrew top can be secured and resecured in pressure-secure fashion.Nevertheless, the shortness of the first thread segments and the usualrounded or smoothed cross-section of the first thread segments enablesthe relatively high thread finish on the opening to be madeuser-friendly, in particular to be made comfortable to the lips of auser drinking directly from the opening.

Preferably, the second thread segments on the inside of the closureskirt define a substantially continuous helical thread path along whichthe first thread segments travel from a substantially fully disengagedto a substantially fully secured position of the closure on the threadedopening. That is to say, the first and second threads do not engage in astepped fashion like a bayonet closure (which is normal for short threadsegments), but rather in a conventional continuous helical screwfashion. In other words, the pitch of the thread path is normally lessthan 90 degrees throughout its length. It will be appreciated that thepitch of the helix may not be constant. Preferably, the mean pitch ofthe helical thread path is from 5 to 20 degrees.

The continuous thread path renders the assembly especially easy to closeby the elderly and infirm, or by children. In contrast, bayonet-typethreads of the kind described in U.S. Pat. No. 5,135,124 require arelatively complex, stepped manipulation to secure the closure onto theopening, with the result that the closure is often inadequately secured.Furthermore, it is extremely difficult to devise a tamper-evident ringfor the closure that separates reliably and easily upon opening of abayonet-type closure assembly. Finally, a continuous thread is easierfor physically weak people to screw down against pressure from insidethe vessel than a bayonet thread.

The second thread segments are not bayonet-type thread segments. Thesecond thread segments extend around the closure skirt a sufficientdistance so that a top portion of one thread segment is proximate to abottom portion of another thread segment, that is to say sufficientlyclose to the adjacent thread segment that the gap between them is toonarrow to allow one of the first thread segments to pass throughvertically. In certain embodiments, respective top and bottom portionsof adjacent second thread segments are circumferentially overlapping.

Preferably, at least one of the second thread segments extends for atleast about 30°, preferably at least 45° around the closure skirt, morepreferably at least 60° around the closure skirt. A thread gap isdefined between the said top and bottom portions of the thread segments.One of the first thread segments travels through this thread gap as theclosure is screwed onto or off the vessel opening.

Preferably, there are eight, twelve or sixteen of the second threadsegments. Preferably the first and second thread segments define afour-start, eight-start or twelve-start substantially continuous andfast-pitched thread path.

Preferably, the closure can be moved from a fully released to a fullyengaged position on the opening (or vice-versa) by a single smoothrotation through about 180 degrees or less, more preferably about 90degrees or less, and most preferably about 45 degrees or less.

Preferably, the maximum radial height of the second thread segmentsabove the cylindrical surface of the closure skirt is greater than about0.1 mm, more preferably greater than about 0.2 mm and still morepreferably from about 0.5 to about 3 mm, most preferably from about 1 toabout 2 mm. Preferably, the width of the second thread segments(measured along the longitudinal axis of the closure skirt) is fromabout 1 mm to about 6 mm, more preferably from about 2 mm to about 4 mm.

The second thread segments are each made up of one or more radiallyspaced projecting portions, each said portion extending radially no morethan about 60° around the closure skirt, preferably no more than about45° around the closure skirt, more preferably from about 2° to about 35°around the closure skirt. The radially spaced projecting portions arepreferably radially spaced apart by gaps extending radially from 0 toabout 10°, preferably from about 0.5° to about 2°. Preferably, the widthof gaps is from about 0.1 mm to about 5 mm, more preferably from about0.5 mm to about 2 mm. In other words, the second thread is preferably abroken or interrupted thread having a plurality of gaps in each threadsegment, but the gaps being sufficiently radially narrow not tointerfere with the operation of the second thread segments. That is tosay, the second thread segments still define a substantially continuoushelical thread path therebetween. This requires the gaps in the secondthread segments (as well as the gaps between the second thread segments)to be radially narrower than the first thread segments.

Preferably, each second thread segment is made up of at least twoportions, preferably at least three or four portions, and this impliespreferably at least one or preferably at least two or three gaps in thethread segment. The presence of the gaps in the second thread segmentsmay improve gas venting through the second thread when openingpressurised containers. More importantly, the closure caps are easier tobump off a one-piece mold mandrel during high speed manufacturing,because the broken threads offer less resistance to radial expansion ofthe closure skirt.

Preferably, at least one of the second thread segments also has asmoothed cross section. The second thread cross section is preferablycomplementary to the cross section described above for the first threadsegments. It will be appreciated that this can result in a better fitbetween the first and second thread segments, for example if they havematching cross-sectional shapes parallel to the axis of rotation.Moreover, tapered or smoothed threads on the closure make it easier tobump the closure off a mold mandrel, thereby assisting high-speedmanufacture of the closures by injection molding without the need formulti-part mold pieces.

The present invention is applicable to a wide variety of drinkingvessels of any shape in which user friendliness is desirable, includingdrinking vessels for both carbonated and non-carbonated beverages. Thepresent invention is applicable to molded thermoplastics containerclosure assemblies, and also to glass or metal container closureassemblies, and to combinations thereof (e.g. a glass vessel with ametal or thermoplastic closure).

Preferably, the container closure assembly according to the presentinvention further comprises complementary locking means on the vesselopening and the closure that resist unscrewing of the closure from thefully engaged position on the opening after the closure has been securedor resecured on the opening until a predetermined minimum opening torqueis applied. These elements enable more steeply pitched threads and freerunning (parallel) threads to be used without risk of the closureunscrewing spontaneously. The use of more steeply pitched threads inturn makes it possible to use wider and higher thread segments withinthe size and height constraints of a normal neck finish.

Preferably, the locking means on the opening comprises a projection orrecess for engagement with a complementary projection or recess on theclosure skirt. More preferably, the projection or recess on the openingis smoothed as hereinbefore defined.

More preferably, the locking means comprise a longitudinal locking ribon the vessel opening, and a complementary locking ramp on the skirtportion of the closure, wherein the locking rib abuts against aretaining edge of the locking ramp when the closure is fully engaged onthe opening. In alternative preferred embodiments, a locking recess suchas a longitudinal groove may be provided in one or more of the first orsecond thread segments, and a longitudinal locking rib is provided onthe other of the opening or on the skirt portion of the closure, wherebythe locking rib is received in the recess in the thread segments at thefully engaged and sealing position of the closure on the opening.Locking means of this kind are described in detail in WO91/18799 andWO95/05322, the entire disclosures of which are expressly incorporatedherein by reference.

The complementary locking means provide a number of importantadvantages. Firstly, they prevent accidental backing off of the closurefrom the fully engaged and sealing position on the vessel due topressure from inside the container. This also permits the use of moresteeply pitched threads. Furthermore, the locking means provide apositive “click” when the fully engaged and sealing position of theclosure is reached, thereby giving the user a positive indication ofthat position. This helps to ensure that exactly the right degree ofcompression is applied between the container and closure to achieve aneffective airtight seal.

Preferably, the container closure assembly according to the invention isan assembly for a carbonated beverage, wherein the container furthercomprises mutually engageable elements on the vessel opening and theclosure to block or restrict rotation of the closure in an unscrewingdirection beyond an intermediate position when the closure is underaxial pressure in a direction emerging from the vessel. This is theso-called pressure safety feature that is intended to prevent theclosure unscrewing uncontrollably or missiling as it is removed from avessel under pressure. Preferably, the preferred embodiments of thispressure safety feature are as described in WO95/05322, WO97/21602 andWO99/19228, the entire contents of which are expressly incorporatedherein by reference.

Preferably, the first and second screw threads are constructed andarranged to permit axial displacement of the closure relative to thevessel opening at least when the closure is at the said intermediateposition, and preferably the engageable elements are adapted to engageeach other when the closure is axially displaced in a direction emergingfrom the opening, for example by axial pressure from inside thepressurized vessel. More preferably, the mutually engageable elementsare constructed and arranged not to mutually engage each other when theclosure is axially displaced in a direction inwardly towards the vesselat the intermediate position, for example when the closure is beingscrewed down onto the vessel opening.

Preferably, the mutually engageable elements comprise a step or recessformed in the upper surface of one of the second screw thread segmentsto provide a first abutment surface against which a second abutmentsurface on one of the first screw thread segments abuts to block orrestrict rotation of the closure in an unscrewing direction at the saidintermediate position when the closure is under axial pressure in adirection emerging from the vessel. (The term “upper” in this contextmeans closer to the base of the closure, i.e. further from the open endof the closure).

More preferably, the second thread segment comprises a first threadportion having a first longitudinal cross section and a second threadportion having a second longitudinal cross section narrower than thefirst cross section, whereby the first thread segment abuts against thesecond thread portion. The relatively broad first cross section ispreferably adjacent to the circumferentially overlapping region of thesecond thread segments, resulting in a relatively narrow thread gap inthat region.

The assemblies according to the present invention preferably furthercomprise additional means for forming a pressure-tight seal between thevessel and the closure. In certain embodiments the sealing meanscomprise a compressible liner inside the base portion of the closure forabutting against a lip of the vessel opening. Preferably, the sealingliner is formed from a compressible elastomer. A circumferential sealingrib may be provided on the lip of the opening, or inside the base of theclosure underneath the sealing liner, in order to optimise compressionof the elastomer to achieve a pressure-tight seal. However, preferably,the lip of the vessel is smooth and rounded in order to optimise itsuser-friendliness.

In other embodiments, the sealing means may comprise a cylindricalsealing plug that projects concentrically and inside the closure skirtand that forms a pressure-tight seal with the inside of the vesselproximate to the opening.

Preferably, the first and second threads on the vessel opening andclosure are variable pitch threads, preferably as described inWO97/21602, the entire contents of which are incorporated herein byreference. Preferably, the pitch of an unscrewing thread path defined bythe first and the second thread segments is relatively lower in a firstregion and relatively higher in a second region displaced from the firstregion in an unscrewing direction. The pitch of the thread path in thefirst region is preferably substantially constant. The first regionnormally includes the position at which the closure is sealed on thevessel. Preferably, the first region extends for about 2° to 40°,preferably 5° to 20° about the circumference of the vessel opening orthe closure skirt. Preferably, the pitch of the lower thread surface inthe first region is in the range of 1° to 12°, more preferably 2° to 8°.

Preferably, the second region is adjacent to the first region of thethread path. Preferably, the pitch of the helical thread path in thesecond region is substantially constant, and the second regionpreferably extends for about 2° to about 35°, preferably for about 5 to15° about the circumference of the container neck or the closure skirt.Preferably, the pitch of the thread path in the second region is in therange of 15° to 35°.

The use of a variable pitch thread renders it easier to combinefast-turn threads having a steep average pitch that are elderly-andchild-friendly with pressure safety. A problem that could arise withfast-turn threads is that they are steeply pitched, which results in atendency to back off from the fully secured position on the vessel whenthe container is pressurized. This problem can be overcome by usingbayonet-type threads, but the use of bayonet-type threads results in anumber of different problems, as described above. In contrast, thevariable pitch threads solve the problem of backing off of the closureunder pressure, whilst retaining all of the advantages of continuous,fast-turn threads.

Preferably, the helical unscrewing thread path further comprises a thirdregion adjacent to the second region, wherein the third region has arelatively low pitch. Preferably, the third region has a relativelyconstant pitch, preferably in the range 1 to 12°, more preferably 2 to8°. The third region preferably includes the position of the closure onthe opening when the closure is blocked at the intermediate gas ventingposition. The relatively low pitch of the third region reduces thetendency of the closure to override the blocking means at high gasventing pressures.

In certain embodiments, the closure assembly includes a recess in theinner surface of the closure skirt, the recess being located between andcircumferentially overlapping two of the plurality of second threadsegments to increase the cross-sectional area provided for gas ventingbetween the second thread segments.

It has been found that the thread gap between overlapping portions ofadjacent second thread segments may have a cross-section that is toosmall for optimal gas venting in all circumstances. The recess overcomesthis difficulty by increasing the cross-section of the thread gap toincrease the rate of gas venting through the thread gap.

The increased cross-sectional area of the venting pathway in thecircumferentially overlapping regions of the second thread permitsfaster venting of pressure from inside the vessel, and thereby reducesthe length of time that the closure is blocked at the intermediateposition while venting takes place, without any loss of pressure safety.

In these embodiments, the recess may comprise an elongate grooveextending around the the closure skirt between the second threadsegments in the said overlapping regions. Preferably, the elongategroove extends substantially parallel to the helical thread path.Preferably, the recess comprises an elongate groove in the inside of theclosure skirt. Preferably, the longitudinal cross-sectional area of therecess is from 5% to 50% of the mean longitudinal cross-sectional areaof the second thread segment portions adjacent to the recess.

Specific embodiments of the drinking vessel closure assemblies accordingto the present invention will now be described further, by way ofexample, with reference to the accompanying drawings, in which:—

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS(S)

FIG. 1 shows a longitudinal cross sectional view of a drinking vesselincorporating a closure assembly according to the present invention withthe closure in the fully engaged position on the vessel opening, andwith a tamper evident ring attached to the closure.

FIG. 2 shows a longitudinal cross sectional view of the drinking vesselof FIG. 1 with the closure resecured on the vessel opening, and with atamper evident ring removed; and

FIG. 3 shows a detail of the closure region of the cross-section of FIG.1 with the first and second thread segments on the back of the assemblyshown in phantom.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, this embodiment is a drinking vessel 1 inthe shape of a drinking glass having a base 2 of diameter about 5 cm anda top 3 of internal diameter about 7 cm and a tubular body 4 of circularcross-section. The aesthetic and practical appeal of such a liquidpackaging format is clear, but it has not hitherto been possible to makea reliable closure assembly for such wide-mouth containers.

The main features of this assembly resemble those of the assemblydescribed and claimed in our International Patent ApplicationsWO95/05322 and WO97/21602 and WO99/19228, the entire contents of whichare expressly incorporated herein by reference. However, it is importantto note that the threads on the closure and the vessel opening arereversed in the present invention relative to the closure assembliesdescribed in those applications. That is to say, the earlier patentspecifications describe in detail assemblies having short threadsegments in the closure skirt and longer thread segments on the neck,whereas the present invention provides only short thread segments on thevessel opening and longer thread segments on the closure skirt.

The assembly is especially suitable for the storage of carbonatedbeverages, such as beer. It includes an opening 10 at the top of thevessel and a closure 12. Both the vessel and the closure are formed fromplastics material. The vessel is preferably formed by injection molding,blow molding and/or thermoforming of polyethylene terephthalate orpolystyrene in the manner conventionally known for such containers. Theclosure is preferably formed by injection molding of polypropylene.

Referring to FIG. 3, the vessel opening 10 is provided with aneight-start first screw thread made up of eight first thread segments18, as shown in FIG. 3. The first thread segments 18 are short threadsegments extending about 10–15 mm around the opening and having a lowersurface with relatively low pitch of about 6° and an upper surface withintermediate pitch of about 13.5°. (The term “upper” in this contextmeans closer to the open end of the vessel). The first thread segments18 present a substantially trapezoidal cross-section along the axis ofthe vessel. The vessel has a rounded lip to enhance theuser-friendliness of the opening.

Referring to FIGS. 1 and 3, the closure 12 comprises a base portion 14and a skirt portion 16. The closure skirt 16 is provided with a secondscrew thread formed from eight second thread segments 20, each having alower thread surface 22 and an upper thread surface 24. (The term“upper” in this context means closer to the base of the closure, i.e.further from the open end of the closure). The upper and lower secondthread surfaces 22, 24 give the thread segments substantiallytrapezoidal side edges that are complementary to the shape of the firstthread segments. A substantially continuous, approximately helicalthread gap 26 is defined between overlapping regions of the said upperand lower surfaces 22, 24 on adjacent second thread segments 20.

An important feature of this assembly is the profiling of the uppersurfaces 24 of the second thread segments 20, which is described in moredetail in our International patent application WO97/21602. The upperthread surfaces 24 in a first, upper region 28 have a substantiallyconstant pitch of only about 6°. The upper region 28 adjoins anintermediate region 30 having a substantially constant, much higherpitch of about 25°. The average pitch of the helical thread path definedby the second thread segments 20 is 13.5°.

The second thread segments 20 also include a pressure safety featuresimilar to that described and claimed in our International PatentApplication WO95/05322. Briefly, the lowermost portion of the secondthread segment 20 defines a step to abut against an end of the firstthread segments 18 and block unscrewing of the closure 12 from theopening 10 when the said first thread segments 18 are in abutment withthe upper surface 24, i.e. when there is a net force on the closure inan axial direction out of the vessel. A third region 34 of the uppersurfaces 24 of the second thread segments situated adjacent to the step32 also has a low pitch of about 6°.

The closure assembly is also provided with complementary lockingelements 38 on the vessel opening and the closure to block unscrewing ofthe closure from the fully engaged position on the vessel unless aminimum unscrewing torque is applied. These locking elements comprisefour equally radially spaced locking ribs on the opening, and fourequally radially spaced retaining ramps on the inside of the closureskirt 16. The ramps comprise a radially sloped outer face and a radiallyprojecting retaining edge against which the rib on the closure abutswhen the closure is fully engaged on the opening. The complementarylocking means may be as described in our International PatentApplication WO91/18799, the entire content of which is hereby expresslyincorporated by reference. However, the locking rib is on the vessel andnot on the closure in this embodiment, which also helps to improve theuser-friendliness of the container neck finish, especially with asuitably smoothed rib.

The closure assembly also comprises means for forming a gas-tight sealbetween the closure and the vessel. This means may comprise a gas-tightelastomeric sealing liner that is compressed against the lip of thevessel. Optimum sealing is preferably achieved when the elastomericsealing liner is compressed to between 30% and 70% of its originalthickness. In other embodiments, sealing may be achieved without theneed for a liner, for example by compression of suitably configuredcircumferential sealing plug, ribs and/or fins on the closure capagainst the opening. Suitable sealing arrangements are described in ourcopending application WO02/42171, the entire content of which isincorporated herein by reference.

The second thread segments 20 terminate at their lower end in aprojecting portion that defines a longitudinal shoulder 72 forming afirst stop against which a second end 74 of the first thread segments 18may abut thereby to block overtightening of the closure.

The closure assembly optionally also comprises a tamper-evident safetyfeature. This comprises a tamper-evident ring 50 that is initiallyformed integrally with the skirt 16 of the container closure 12 andjoined thereto by frangible bridges. The tamper-evident ring 50comprises a plurality of integrally formed, flexible, radially inwardlypointing retaining tabs. A circumferential retaining lip 56 is providedon the vessel opening 10. Ratchet projections (not shown) may also beprovided on the vessel below the circumferential retaining lip 56 andradially spaced around the opening to block rotation of thetamper-evident ring 50 on the opening 10 in an unscrewing direction.However, it may be preferred to smooth or omit the ratchet projectionsin order to improve user-friendliness of the vessel opening finish. Thestructure and operation of the tamper-evident ring feature are asdescribed and claimed in our International Patent ApplicationWO94/11267, the entire contents of which are expressly incorporatedherein by reference.

In use, the closure 12 is secured onto the vessel opening 10 by screwingdown in conventional fashion. The closure 12 can be moved from a fullydisengaged position to a fully engaged position on the vessel byrotation through about 45°. When the closure is being screwed down,there is normally a net axial force applied by the user on the closureinto the vessel, and accordingly the first thread segments 18 abutagainst and ride along the upper surfaces 22 of the projecting portionsof the second thread segments 20 on the closure skirt. It can thus beseen that the first thread segments follow a substantially continuouspath along a variable pitch helix. The first and second threads arefree-running, which is to say that there is substantially no frictionaltorque between the thread segments until the fully engaged position isneared. These features of a 45° closure rotation, substantiallycontinuous thread path and free-running threads all make the closureextremely easy to secure and resecure, especially for elderly orarthritic persons, or children.

As the closure nears the fully engaged position on the vessel opening10, several things happen. Firstly, the tamper-evident ring 50 starts toride over the retaining lip 56 on the vessel opening. The retaining tabson the tamper-evident ring 50 flex radially outwardly to enable thetamper-evident ring to pass over the retaining lip 56 without excessiveradial stress on the frangible bridge.

Secondly, the locking ribs on the vessel opening ride up the outerramped surface of the retaining ramps on the closure skirt 16. Thegentle slope of the ramped surfaces, together with the resilience of theclosure skirt 16, mean that relatively little additional torque isrequired to cause the locking ribs to ride up the ramped surfaces.

Thirdly, the initial abutment between the sealing liner or other sealingmeans in the container closure base and the sealing lip 48 on the vesselresults in a net axial force on the closure in a direction out of thevessel. This pushes the thread segments 18 out of abutment with thelower surfaces 22 of the projecting portions of the second threadsegments 20 and into abutment with the upper surfaces 24 of theprojecting portions of the second thread segments 20. More specifically,it brings the first thread segments 18 into abutment with the upperregions 28 of the projecting portions of the upper thread surfaces 24.Continued rotation of the closure in a screwing-down direction causesthe first thread segments 18 to travel along the upper regions 28 untilthe final, fully engaged position shown in FIG. 3 is reached. The lowpitch of the upper surfaces 28 means that this further rotation appliespowerful leverage (camming) to compress the sealing liner against thesealing rib 48 in order to achieve an effective gas-tight seal.

When the fully engaged position of the closure 12 on the vessel opening10 is reached, the locking ribs click over the top of the respectiveramped surfaces 40 and into abutment with the steep retaining surfacesof the ratchet ramps. At the same position, the second ends 74 of thefirst thread segments 18 may come into abutment with the stop shoulders72 at the top of the second thread segments, thereby blocking furthertightening of the closure than could damage the threads and/orover-compress the sealing liner.

When the closure 12 is in the fully engaged position on the vesselopening 10, the upper surfaces of the first thread segments 16 abutagainst the upper regions 28 of the upper thread surfaces 24 of theprojecting portions of the second thread segment 20, as shown in FIG. 3.The upper surface of the first thread segments has a low pitch to matchthat of the upper regions 28, so as to maximise the contact area betweenthe projecting portions in the regions 28, and thereby distribute theaxial force exerted by the closure as evenly as possible around thevessel opening. Because of the low pitch in the regions 28, relativelylittle of the axial force emerging from the vessel due to pressureinside the vessel is converted into unscrewing rotational force by theabutment between the thread surfaces in this position. This greatlyreduces the tendency of the closure to unscrew spontaneously underpressure. Spontaneous unscrewing is also prevented by the abutmentbetween the locking ribs and the retaining edge on the locking ramps. Animportant advantage of the assembly is that the reduced tendency tounscrew spontaneously due to the low pitch of the thread in the lowerregions 28 means that the minimum opening torque of the locking elements38 can be reduced without risk of the closure blowing off spontaneously.This makes the closure easier to remove by elderly or arthritic people,or by children, without reducing the pressure safety of the closure.

In use, the closure is removed from the vessel by simple unscrewing. Aninitial, minimum unscrewing torque is required to overcome theresistance of the locking elements 38. Once this resistance has beenovercome, essentially no torque needs to be applied by the user tounscrew the closure. The internal pressure inside the vessel exerts anaxial force on the closure in a direction emerging from the vesselopening, as a result of which the first thread segments 18 ride alongthe upper surfaces 28 of the projecting portions of the second threadsegments 20 as the closure is unscrewed. The first thread segmentsinitially ride along the upper regions 28, and then along the steeplypitched intermediate regions 30 of the upper surface of the secondthread segments 20. The first thread segments 18 then come into abutmentwith lower projecting portion 32 of the second thread segments 20. Inthis position, further unscrewing of the closure is blocked while gasventing takes place along the thread paths 26. It should also be notedthat, in this intermediate gas venting position, the first threadsegments 18 abut primarily against the region 34 of the upper surface ofthe second thread segments 20. The low pitch of this region 34 resultsin relatively little of the axial force on the closure being convertedinto unscrewing rotational torque, thereby reducing the tendency of theclosure to override the pressure safety feature and blow off.

Once gas venting from inside the vessel is complete so that there is nolonger axial upward force on the closure, the closure can drop down soas to bring the thread segments 18 into abutment with the lower surfaces22 of the second thread segments 20. In this position, unscrewing can becontinued to disengage the closure completely from the vessel.

The above embodiment has been described by way of example only. Manyother embodiments of the present invention falling within the scope ofthe accompanying claims will be apparent to the skilled reader. Inparticular, the present invention is not limited to closure assembliesfor drinking vessels, or to containers formed from moldedthermoplastics.

1. A threaded closure assembly for a wide mouth vessel, said assemblycomprising: a vessel opening; a closure for said opening, the closurehaving a base portion and a skirt portion; a first screw thread on theopening, said first screw thread comprising one or more first threadsegments; a second screw thread on an inner surface of the skirt of theclosure, said second screw thread comprising one or more second threadsegments; said first and second screw threads being configured to enablea user to secure, remove and resecure the closure into a sealingposition on the opening by rotation of the closure on the opening by acontinuous smooth rotation through about 90° or less; wherein said firstthread segments are shorter than said second thread segments; andwherein the second thread segments are each made up of one or morecircumferentially spaced projecting portions, each said portionextending circumferentially no more than about 60° around the closureskirt the second thread segments forming a substantially continuoushelical thread path.
 2. A closure assembly according to claim 1, whereinthe vessel has a base and substantially tubular side walls, and thecross-sectional area of the opening is at least 50% of thecross-sectional area of the base.
 3. A closure assembly according toclaim 1, wherein there are four or more of said first thread segments.4. A closure assembly according to claim 1, wherein at least one of thefirst thread segments extends circumferentially from 5 mm to 30 mmaround the container neck.
 5. A closure assembly according to claim 4,wherein at least one of the first thread segments extendscircumferentially from 10 mm to 20 mm around the container neck.
 6. Aclosure assembly according to claim 1, wherein at least one of the firstthread segments has an upper or a lower surface with a mean pitch offrom 5° to 25°.
 7. A closure assembly according to claim 1, wherein atleast one of the first thread segments has an upper or a lower surfacewith a constant pitch region extending for at least 10 mm around thevessel opening.
 8. A closure assembly according to claim 1, wherein atleast one of the second thread segments extends for at least 45° aroundthe closure skirt.
 9. A closure assembly according to claim 1, whereinat least one of the second thread segments is made up of two or moreprojecting portions.
 10. A closure assembly according to claim 1,wherein the radially spaced projecting portions each extend less thanabout 45° around the closure skirt.
 11. A closure assembly according toclaim 1, wherein the radially spaced projecting portions are radiallyspaced apart by gaps extending radially from 0 to about 10°.
 12. Aclosure assembly according to claim 1, wherein the maximum radial heightof the first and/or the second thread segments is from about 0.5 toabout 3 mm.
 13. A closure assembly according to claim 1, furthercomprising mutually engageable elements on the vessel opening and theclosure to block or restrict rotation of the closure in an unscrewingdirection beyond an intermediate position when the closure is underaxial pressure in a direction emerging from the vessel.
 14. A closureassembly according to claim 1, wherein the second thread segments definea substantially continuous helical thread path along which said firstthread segments travel from a substantially fully disengaged to asubstantially fully secured position of the closure on the vessel.
 15. Aclosure assembly according to claim 14, wherein the mean pitch of saidhelical thread path is from 5 to 20 degrees.
 16. A closure assemblyaccording to claim 1, wherein the second thread segments define at leastone recess for receiving said first thread segments, said recess beingsubstantially helical and extending for more than 30 degrees around theclosure skirt.
 17. A closure assembly according to claim 1, whereinthere are four or more of the second thread segments.
 18. A closureassembly according to claim 1, wherein at least one of the second threadsegments has a smoothed cross section.
 19. A closure assembly accordingto claim 1, wherein the first thread segments have a cross-section alongthe longitudinal axis of the assembly that is rounded, chamfered,trapezoidal or triangular.
 20. A closure assembly according to claim 1,wherein the closure can be moved from a fully released to a fullyengaged position on the vessel by a single smooth rotation through about90 degrees or less.
 21. A closure assembly according to claim 20,wherein the closure can be moved from a fully released to a fullyengaged position on the vessel by a single smooth rotation through about60 degrees or less.
 22. A closure assembly according to claim 21,wherein the closure can be moved from a fully released to a fullyengaged position on the vessel by a single smooth rotation through about45 degrees or less.
 23. A closure assembly according to claim 1, furthercomprising complementary locking means on the vessel opening and theclosure that resist unscrewing of the closure form the fully engagedposition on the vessel after the closure has been secured or resecuredon the vessel until a predetermined minimum opening torque is applied.24. A closure assembly according to claim 23, wherein the locking meanson the vessel opening comprises a projection or recess for engagementwith a complementary projection or recess on the closure skirt.
 25. Aclosure assembly according to claim 1, wherein the vessel is formed froma material selected from the group consisting of thermoplastics, glass,metal, and combinations thereof.
 26. A closure assembly according toclaim 1 in which the first thread segments comprise helical threadsegments having rounded ends.